Hyperbranched chemoselective silicon-based polymers for chemical sensor applications

ABSTRACT

The invention provides a device for selective molecular recognition, the device comprising a sensing portion, wherein said sensing portion includes a substrate having coated thereon a layer comprising a hyperbranched compound having:  
     (1) a polymer backbone portion that is at least partly randomly branched;  
     (2) at least one pendant group extending from the polymer backbone portion; and  
     (3) at least one halogen substituted alcohol or phenol group substituted at the pendant group(s) of the polymer backbone portion.  
     The compound of the invention preferably has the general formula:  
                 
 
     wherein A is the hyperbranched backbone portion of the polymer;  
     L and M are independently selected pendant groups of said polymer backbone;  
     X and Y are independently selected halogen substituted alcohol or phenol groups;  
     q and r are independently selected and at least 1; and  
     n is at least 3.  
     The device is used to detect the molecules of a hydrogen bond accepting vapor such as organophosphorus or nitroaromatic species.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to the detection of noxiouschemical species by means of chemoselective hyperbranched polymericcompounds. More particularly, the invention relates to the detection oftoxic or explosive chemical vapors, such as chemical agents ornitro-substituted species, respectively, by sorbent materials comprisingchemoselective hyperbranched polymeric molecules.

[0003] 2. Description of Related Art

[0004] Determining and/or monitoring the presence of certain chemicalspecies within an environment, e.g., pollutants, toxic substances andother predetermined compounds, is becoming of increasing importance withrespect to such fields as health, environmental protection, resourceconservation, and chemical processes. Devices for the molecularrecognition of noxious species or other analytes typically include (1) asubstrate and (2) a molecular recognition coating upon the substrate.These devices may be used, for example, in chemical vapor sensing or theselective separation of gases by gas chromatography. Small molecularrecognition devices are described in Grate et al., Sensors and ActuatorsB, 3, 85-111 (1991) and Grate et al., Analytical Chemistry, Vol. 65, No.14, Jul. 15, 1993, both of which are incorporated herein by reference.

[0005] Frequently, the substrate is a piezoelectric material or awaveguide, which can detect small changes in mass. One illustrativeexample of a device relying upon molecular recognition as a surface isknown as a surface acoustic wave (SAW) sensor. SAW devices function bygenerating mechanical surface waves on a thin slab of a piezoelectricmaterial, such as quartz, that oscillates at a characteristic resonantfrequency when placed in a feedback circuit with a radio frequencyamplifier. The oscillator frequency is measurably altered by smallchanges in mass and/or elastic modulus at the surface of the SAW device.

[0006] SAW devices can be adapted to a variety of gas-phase analyticalproblems by designing or selecting specific coatings for particularapplications. The use of chemoselective polymers for chemical sensorapplication is well established as a way to increase the sensitivity andselectivity of a chemical sensor with respect to specific classes ortypes of analytes. Typically, a chemoselective polymer is designed tocontain functional groups that can interact preferentially with thetarget analyte through dipole-dipole, Van der Waal's, or hydrogenbonding forces. For example, strong hydrogen bond donatingcharacteristics are important for the detection of species that arehydrogen bond acceptors, such as toxic organophosphorus compounds.Increasing the density of hydrogen bond acidic binding sites in thecoating of a sensor results in an increase in sensitivity.

[0007] Chemoselective films or coatings used with chemical sensors havebeen described by McGill et al. in Chemtech, Vol. 24, No. 9, 27-37(1994). The materials used as the chemically active, selectivelyabsorbent layer of a molecular recognition device have often beenpolymers, as described in Hansani in Polymer Films in SensorApplications (Technomic, Lancaster, Pa. 1995). For example, Ting et al.investigated polystyrene substituted with hexafluoroisopropanol (FFIP)groups for its compatibility with other polym rs in Journal of PolymerScience: Polymer Letters Edition, Vol. 18, 201-209 (1980) Later, Changet al. and Barlow et al. investigated a similar material for its use asa sorb nt for organophosphorus vapors, and examined its behavior on abulk quartz crystal 2 monitor device in Polymer Engineering and Science,Vol. 27, No. 10, 693-702 and 703-15 (1987). Snow et al. (NRL 3 LetterReport, 6120-884A) and Sprague et al. (Proceedings of the 1987 U.S. ArmyChemical Research Development and Engineering Center ScientificConference on Chemical Defense Research, page 1241) reported makingmaterials containing HFIP that were based on polystyrene andpoly(isoprene) polymer backbones, where the HFIP provided stronghydrogen bond acidic properties. These materials were used as coatingson molecular recognition devices, such as SAW sensors, and showed highsensitivity for organophosphorus vapors. However, both the parentpolymers and the HFIP-containing materials were glassy or crystalline atroom temperature. Because vapor diffusion may be retarded in glassy orcrystalline materials, the sensors produced were slow to respond andrecover. Further, these are polymeric materials and, like all polymers,they can vary significantly from batch to batch in precise composition,purity and yield. Additional information is reported in Polymn Eng. Sci,27, 693 and 703-715 (1987).

[0008] Vicari et al., U.S. Pat. No. 6,114,489, issued Sep. 5, 2000,discloses reactive hyper-branched polymers containing terminal hydroxy,carboxy, epoxy, and isocyanate groups. The compounds are useful ascomponents in powder coating compositions for the formation of hard,impact resistant films. Examples of the preferred hyperbranchedpolyesters are those formed from α,α-bis(hydroxymethyl)-propionic acid.The backbone of these hyperbranched polymers are composed of polyesterunits.

[0009] Okawa et al., U.S. Pat. No. 6,140,525 issued Oct. 31, 2000,discloses a class of hyperbranched polymers that are prepared bycontacting macromonomers that have both silicon hydride and unsaturatedorganic terminal groups with group VIII metal catalysts. Thehyperbranched polymers are useful as surfactants, gelling agents, drugdelivery systems, and polymeric absorbents. The hyperbranched polymerbackbones are comprised of a combination of siloxane and carbosilanesegments. Examples of preferred macro-monomers include(HSi(CH₃)₂O)₂Si(CH₃)OSi(CH₃)₂(CH₂)₂(Si(CH₃)₂O)_(n)Si(CH₃)₂CH═CH₂, wheren is 10 to 100.

[0010] Decker et al., U.S. Pat. No. 6,001,945, issued Dec. 14, 2001,discloses hyperbranched polymers containing silicon atoms and a methodof making these materials. The exchange (condensation) reaction thatforms the hyperbranched polymers results in the elimination of analcohol by-product and the formation of hyperbranched polymer backbonescomprised of siloxane linkages.

[0011] The inventors have now discovered a class of hyperbranchedmolecules that can be used to produce hydrogen bond acidic coatings forchemical sensor applications. Using the hyperbranched molecules that arehighly functionalized results in significant sensitivity improvements.Further, the chemoselective hyper-branched molecules of the presentinvention exhibit, not only improved sensitivity to organophosphorusspecies, but also high selectivity and sensitivity towardnitro-substituted chemical vapors, and are thus also useful fordetecting the presence of explosives. Conventional explosives, such astrinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX),and octahydro-1,3,5-trinitro-1,3,5,7-tetrazocine (Hi), may be containedin unexploded munitions, e.g., buried below the surface of the ground.Such munitions exude or leak vapors of the explosive. These vapors aretypically concentrated in the surrounding soil and then migrate to thesurface where they can be detected by the compounds, devices and methodsof the invention.

SUMMARY OF THE INVENTION

[0012] According to a first aspect of the present inv ntion, there isprovided a hyperbranched polymeric compound having; (1) a polymerbackbone portion that is at least partly randomly branched; (2) at leastone pendant group extending from the polymer backbone portion; (3) andat least one halogen substituted alcohol or phenol group substituted atthe pendant group(s) of the polymer backbone portion.

[0013] According to a second aspect of the invention, there is provideda device for selective molecular detection, the device comprising asensing portion, wherein the sensing portion includes a substrate havingcoated thereon a layer, the layer comprising the hyperbranched compoundof the invention.

[0014] According to another aspect of the invention, there is provided amethod of detecting a hydrogen bond accepting vapor, such as anitroaromatic vapor, comprising the steps of:

[0015] (a) contacting the molecules of such a vapor with the sensingportion of the device of the invention;

[0016] (b) collecting the molecules in the layer of the device, themolecules altering a specific physical property of the layer; and

[0017] (c) detecting the amount of change with respect to the physicalproperty from before the contacting step (a) and after the collectingstep (b).

[0018] According to yet another aspect of the invention, there isprovided a solution for preparing a chemical vapor sensor comprising (a)an amount of the hyperbranched compound of the invention effective toenhance the sensitivity of the sensor to hydrogen bond accepting vaporssuch as chemical agents or nitroaromatic compounds and (b) a solvent forthe hyperbranched compound.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 shows an example of a hyperbranched compound of theinvention, here, a hyperbranched polycarbosilane with fluoroalcoholfunctionalized allyl groups.

[0020]FIG. 2 shows another example of a hyperbranched compound of theinvention, here, a hyperbranched polycarbosilane with fluoroalcoholfunctionalized phenyl and allyl groups.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The hyperbranched molecules of the invention are polymericmolecular constructions having a randomly branched backbone portion withattached pendant groups. The randomly branched backbone portion of themolecule may be composed of linear, branched, and dendritic units, whichmay themselves be further branched, forming the backbone portion of thehyperbranched polymer molecule. The detailed chemical structure of thehyperbranched backbone may dominate certain polymer physical properties.Hyperbranched polymers may be distinguished from dendritic, branched,and linear polymers in that:

[0022] (a) The degree and distribution of branching in a hyperbranchedpolymer is variable and, therefore, the molecular weight of thehyperbranched materials usually occurs over a broad distribution while adendrinmer has a precise structure and molecular weight;

[0023] (b) The chemical synthesis of a hyperbranched polymer may becarried out in a single step from the starting monomer, whereas thesynthesis of a dendritic polymer requires a multistep syntheticprocedure;

[0024] (c) Linear polymers are not branched; and

[0025] (d) Branched polymers are branched in a regular fashion whereashyperbranched polymers are branched in a random fashion.

[0026] Although not bound by theory, it is believed that thehyperbranched morphology offers advantages over linear macromoleculeswith the same or similar repeating units because the randomly branchedstructure imposes particular physical properties such as reduced polymerchain entanglement, lower glass transition and melting temperatures andincreased availability of terminal functional groups. These constraints,often including steric crowding, inhibit even very long chains frompacking in their thermodynamically preferred conformations forcrystallization, and thereby lower their melting points due to entropicfactors. The random variation in structure that occurs withhyperbranched materials is also a contributing factor to the bulkproperties of these materials. By controlling the structure of thehyperbranched polymer, for example, with suitable ratios of branchingarm length to average branch multiplicity, the free volume available tothe chain ends can be made relatively large. In this case, a large freevolume at the chain ends may facilitate arm segmental motion, althoughthis effect is often negated by steric crowding at the terminal groups.

[0027] The compound of the invention is a hyperbranched polymericcompound having; (1) a polymer backbone portion that is at least partlyrandomly branched; (2) at least one pendant groups extending from thepolymer backbone portion; (3) and at least one halogen substitutedalcohol or phenol group substituted at the pendant group(s) of thepolymer backbone portion. The compound may be entirely organic ororganometallic in composition. Preferred compounds can be represented bythe general formula:

[0028] wherein A is the hyperbranched backbone portion of the polymer;

[0029] L and M are independently selected pendant groups of the polymerbackbone;

[0030] X and Y are independently selected halogen substituted alcohol orphenol groups;

[0031] q and r are independently selected and at least 1, preferablyranging from 1 to about 10; and

[0032] n is at least 3, preferably ranging from 20 to 100,000.

[0033] A, the hyperbranched backbone portion of the compound, may becomposed of repeating units consisting of a single atom such as a carbonor silicon atom; a hydrocarbon moiety; an organometallic fragment orcluster; or a silicon based moiety such as a siloxane, carbosilane, orsilylene moiety; or a combination thereof. Examples of useful “A”backbone repeat units include {Si—(-Z)_(x)}, {C—(-Z)_(x)}, Fe(—C₅H₄Z-)₂,C₆H_(n)(-Z)_(6-n), and the like, wherein Z is a hydrocarbon, silylene,carbosilane, siloxane, or carbosiloxan fragment of 1 to 20 atoms inlength, including but not limited to alkylene, alkenylene, alkynylene,cycloalkylene, cycloalkenylene, arylene, or heterocyclene. Preferably,however, A is {Si-(alkylen-)}, {Si-(arylene-)}, or {Si-(alkenylene-)}.Most preferably, A is {Si[(CH₂)_(x)]} wherein x is 1 to 3.

[0034] L and M in the above formula are independently selected pendantgroups that extend from the hyperbranched backbone portion of thecompound. L or M may be saturated or unsaturated. By “unsaturated” ismeant any site of unsaturation, such as, for example, a double or triplebond or an aromatic ring. L or M may be entirely hydrocarbon or maycontain one or more heteroatoms, such as, for example, Si, N, O, S, F,Cl, Br and the like, and may contain further branching entities. Forexample, L or M may independently be alkylene, alkenylene, alkynylene,arylene, alkylene-arylene, alkenylene-arylene, alkynylene-arylene,—C-(alkenylene)₃, —Si-(alkenylene-)₃, —N-(alkenylene-)₂, or—SiO-(alkenylene-)₃, where alkenylene is as defined above;—C-[alkylene-Si-(alkenylene)₃]₃, —Si-[alkylene-C-(alkenylene)₃]₃,—Si-[allylene-Si-(alkenylene)₃]₃, —SiO-[alkylene-Si-(alkenylene)₃]₃,—CO-falkylene-Si-(alkenylene)₃, —Si-[alkylene-N-(alkenylene)₃, wherealkylene and alkenylene are defined as above; —C-(cycloalkenylene-)₃,—Si-(cycloalkenylene-)₃, and CON-(cycloalkenylene-)₃, wherecycloalkenylene is defined as above;—C-[cycloalkylene-Si-(alkenylene)₃]₃,—Si-[cycloalkylene-C-(alkenylene)₃]₃,—Si-[cycloalkylene-Si-(alkenylene)₃]₃,—SiO-Ccycloalkylene-Si-(alkenylene)₃]₃,—CO-[cycloalkylene-Si-(alkenylene)₃]₃,—Si-[cycloalkylene-N-(alkenylene)₂]₃, where cycloalkylene and alkenyleneare defined as above; —C-(arylene-)₃, —Si-(arylene-)₃, and—SiO-(arylene-)₃, where arylene is defined as above;—C-(heterocyclene-)₃, —Si-(heterocyclene-)₃, and —SiO-(heterocyclene-)₃,where heterocyclene is as defined above;—C-[alkylene-Si-(alkylene-arylene)₃]₃,—Si-[alkylene-C-(alkylene-arylene)₃]₃,—Si-[alkylene-Si-(alkylene-arylene)₃]₃,—SiO-[alkylene-Si-(alkylene-arylene)₃]₃,—CO-[alkylene-Si-(alkylene-arylene)₃]₃,—Si-[alkylene-N-(alkylene-arylene)₂]₃, where alkylene or arylene aredefined as above.

[0035] Preferably, however, L and M are independently an alkenylene,aklylene-arylene, alkeneylene-arylene, -[alkylene-Si-(alkenylene)₃]₃ oran -[alkylene-Si-(alkylene-arylene)₃]₃ group. Even more preferably, Land M are independently —(CH₂)_(m)—, —(CH═CH—CH₂)—, —[(CH₂)_(m)C₆H₄]—,—[(CH₂)_(m)—S—(CH═CH—CH₂—)₃]₃ or —Si—[(CH₂)_(m)—Si—[—(CH₂)_(n)—C₆H₄—]₃}₃wherein m and n are independently 1 to 6.

[0036] The novel compounds of the invention are strongly hydrogen bonddonating. They are useful in a variety of applications, especially as acoating material on chemical sensors. They are very sensitive forhydrogen bond accepting vapors such as organophosphorus andnitro-substituted compounds such as a those in a great number ofwell-known toxic and explosive materials, respectively.

[0037] The compounds of the invention can be synthesized by reactinghexafluoroacetone with the parent hyperbranched molecule, comprising ahyperbranched backbone A and a number of pendant unsaturated groups,taking advantage of the reactivity of perfluoroketones with terminallyunsaturated groups, as described by Urry et al., J. Org. Chem, 1968, 33,2302-2310, hereby incorporated by reference. Alternatively, thecompounds of the invention can be synthesized by reactinghexafluoroacetone with the parent hyperbranched molecule, comprising ahyperbranched backbone A and a number of pendant groups containingmetalated sites, followed by protonation, as described by Barbarich eral., J. Am. Chem. Soc., 1999, 121, 4280-4281, hereby incorporated byreference. Two such hyperbranched compounds of the invention are shownin FIGS. 1 and 2. Using known methods (see, for example, Whitmarsh, C.K., Interrante, L. V. Organometallics, 1991, 10, 13361344; Uhlig, W. J.Polym. Sci., Part A: Polym. Chem., 1998, 36,725-735 and Koopman, F.,Frey, H. Macromolecules 1996,29, 3701-3706.) these compounds aretypically synthesized in moderate to high yield.

[0038] Once synthesized, th se functionalized hyperbranched compoundscan be coated to a controlled film thickness on a substrate, eitheralone or mixed with a solvent or similarly functionalized molecule.Useful substrates include planar chemical sensors, such as surfaceacoustic wave (SAW) substrates; silica optical fibers; microcantileversand other MEMS devices, and the interior surfaces of silica capillaries.The substrate chosen is based on the sensing mechanism being used.

[0039] The principle of operation of an acoustic wave device transducerinvolves the production of an acoustic wave that is generated on thesurface or through the bulk of a substrate material and allowed topropagate. To generate an acoustic wave typically requires apiezoelectric material. Applying a time varying electric field to thepiezoelectric material will cause a synchronous mechanical deformationof the substrate with a coincident generation of an acoustic wave in thematerial. The time varying electric field is generated in the surface byapplying a time varying electrical field through one or more electrodes,which are connected to the piezoelectric material via one or more metalwire bonds and to an electrical circuit. Another electrode or electrodesreceives the wave at a distance from the first electrode or electrodes.The second electrode or electrodes is also connected via metal wirebonds to the electrical circuit and the piezoelectric material. Suchdevices are operable in a frequency range of about 2 kilohertz to 10gigahertz, preferably from about 0.2 megahertz to about 2 gigahertz and,more preferably, in the range of between about 200 to 1000 megahertz.

[0040] For piezoelectric sensors, piezoelectric substrates well-known inthe art, such as ST-ut quartz, are useful in accordance with theinvention. In addition to quartz crystals, piezoelectric ceramics, suchas those of the barium titanate and lead zirconium titanate families,are suitable substrates. These include, for example, LiNbO₃; BaTiO₃; 95wt. % BaTiO₃/5% GaTiO₃; 80 wt. % BaTiO₃/12% PbTiO₃/8% CaTiO₃; PbNb₂O₆;Na_(0.5)K_(0.5)NbO₃; Pb_(0.94)Sr_(0.06)(Ti_(0.48)Sr_(0.52))O₃; andPb_(0.94)(Ti_(0.48)Sr_(0.52))O₃. In some cases, the substrate maycomprise a piezoelectric coating material, such as ZnO or AIN, appliedto a non-piezoelectric material, such as silicon. The piezoelectricproperties of these and other suitable materials are provided in CRCHandbook of Materials Science, Vol. III, Charles T. Lynch, CRC Press:Boca Raton, 198 (1975).

[0041] The sensing portion of an acoustic wave device of the inventionis the area under the chemoselective layer where the chemoselectivelayer covers the transducer. The area of the sensing portion of such adevice can be on the order of cm² to μm².

[0042] An optical waveguide chemical sensor consists of a light source,an optical waveguide, a chemoselective film or layer, and a detector toanalyze the light after interacting with the layer. The waveguide isused to propagate light to a sensing portion of the device that containsthe chemoselective layer. The light travels towards this coating andinteracts with it. If the analyte being detected is present in thelayer, the optical characteristics of the light may be altered, and thechange is detected by an optically sensitive detector.

[0043] Useful optical chemical s nsors, commonly referred to asoptrodes, typically include light sources such as semiconductor lasers,light-emitting diodes, or halogen lamps; optical waveguides such asfiber optics or planar waveguide substrates; chemoselective layersdeposited on the sensing portion of the optrode exposed to an analyte;and detectors for monitoring the optical characteristics of an optrode.Sorption of the analyte to the chemoselective layer modifies the opticalcharacteristics of the optrode, and this is usually detected as a changein refractive index or light intensity at one or more wavelengths oflight. Thus, for optical sensors, both optical fibers and opticalwave-guides are well-known in the art and useful in the presentinvention.

[0044] Fiber optic waveguides for sensor applications are commonlymanufactured from silica glass or quartz as the core of the fiber.Surrounding this core is a cladding material that exhibits a lowerrefractive index than the core to achieve internal reflectance.Chemoselective layers are typically applied at the distal tip of a fiberoptic or along the side of the fiber optic where a portion of thecladding material has been removed.

[0045] Planar waveguide optical sensors use planar substrate devices aslight guides. The use of a planar waveguide normally involves the use ofevanescent wave techniques to take advantage of the large active surfacearea available. Many of these sensors use the fluorescent properties ofa chemoselective layer and are thus called Total Internal ReflectionFluorescence (TIRF) sensors.

[0046] Preferably, acoustic wave devices are used as the substrate forthe device of the invention. Particularly preferred are SAW devices suchas 915 MHz two-port resonators made of ST-cut quartz with aluminummetallization and a thin silicon dioxide overcoat. SAW resonators andoscillator electronics to drive them are commercially available fromRFM, Dallas, Tex.

[0047] Before applying a coating to form the sensor portion of thedevice of the invention, the substrate is usually cleaned. The cleaningprocedure typically involves rinsing the device in an organic solventand then subjecting it to plasma cleaning, as is well known. Optionally,the substrate can be silanized with a material such asdiphenyltetramethyldisilazane (DPTMS) by immersing the cleaned substratesurface in liquid DPTMS and then placing the immersed surface into apartially evacuated chamber heated to about 170° C. for about 12 hours.The silanized substrate is then removed and solvent cleaned with, forexample, toluene, methanol, chloroform, or a physical or serialcombination thereof, before applying the chemically sensitive sensorlayer of the device.

[0048] The method used for coating the compounds of the invention onto asubstrate is not critical, and various coating methods known in the artmay be used. Typically, the coating is applied to the substrate insolution, either by dipping, spraying or painting, preferably by anairbrush or spin coating process. Laser deposition techniques may alsobe used, particularly when coating MEMS devices. The concentration ofthe compound of the invention in the coating solution should besufficient to provide the viscosity most appropriate for the selectedmethod of coating, and may easily be determined empirically.

[0049] The solvent used, although not critical, should be sufficientlyvolatile as to facilitate quick and easy removal, but not so volatile asto complicate the handling of the coating solution prior to beingdeposited on the substrate. Examples of useful organic solvents include,for example, hexane, chloroform, dichloromethane, toluene, xylenes,acetonitrile and tetrahydrofuran. J. W. Grate and R. A McGill inAnalytical Chemistry, Vol. 67, No. 21, 4015-19 (1995), the subject ofwhich is hereby incorporated by reference, describe making chemicalacoustic wave detectors by applying a thin film to a surface acousticwave device. The thickn ss of the chemoselective layer preferably doesnot exceed that which would reduce the frequency of a chemical sensoroperating at 250 megahertz by about 250 kilohertz and, typically, is inth range of about 0.5 nr to 10 microns, preferably in the range of 5 to500 nm.

[0050] The coating may comprise a single layer or multiple layers. Withmultiple layers, a layer containing the compound of the invention may becombined with at least one other layer that provides pores suitable forphysically eliminating some chemical species of large size that are notto be monitored.

[0051] The process of sorption plays a key role in the performance ofchemical sensors for gas phase analysis. For example, microsensors,which consist of a physical transducer and a selective sorbent layer,sense changes in the physical properties, such as mass, of the sorbentlayer on the surface of the transducer, due to the sorption of analytemolecules from the gas phase into the sorbent layer. Coating propertiesthat are known to elicit a detectable SAW sensor response are mass(i.e., as determined by the thickness and density of the coating),elasticity, viscoelasticity, conductivity, and dielectric constant.Changes in these properties can also result in changes in theattenuation (i.e., loss of acoustic power) of the wave. In somesituations, monitoring the attenuation may be preferable to monitoringthe velocity of a wave. Alternatively, there are some situations wheresimultaneously monitoring both velocity and attenuation can be useful.In any event, it is the modification of the sensed properties of thesorbent layer, as a result of sorption, that results in the detection ofanalyte molecules in the gas phase. SAW devices coated with compounds ofthe invention are capable of detecting mass changes as low as about 100pg/mr². The vapor diffusion rate into and out of the polymer film isgenerally rapid, but does depend upon the thickness of the polymer film.

[0052] Sensor selectivity, the ability to detect a chemical species inan environment containing other chemical species, is generallydetermined by the ability of the coated layer to specifically sorb thespecies to be detected to the exclusion of almost all others. For mostcoatings, selectivity is obtained based on providing stronger chemicalinteractions between the coated layer and the target species than occursbetween the layer and species that are not to be detected. The method ofselectively detecting the presence of a chemical entity within anenvironment comprises (a) placing the sensing portion of the device ofthe invention in the environment and (b) detecting changes in the coatedlayer of the sensing portion of the device. The environment may begaseous or liquid.

[0053] More than one device may be provided. For example, a plurality ofsensor portions could be used in a sensor array with, e.g., associatedcontrol devices and software, in a manner similar to conventionalprocedures employing sensor arrays.

[0054] After an initial sensing has taken place, the coated sensor layercan be purged or cleaned by a second stream, allowing the sensing of anew third stream to take place. For example, for liquid sensingapplications, water- or acid-base solutions could be used as purging orcleaning solutions, depending upon the species being detected and thenature of the layer. For gas applications, dry nitrogen or clean aircould be used as a cleaning stream.

[0055] In the devices and methods of the invention, the compounds aregood sorbents for basic vapors, such as organophosphorus andnitro-substituted compounds. It is expected that the devices of theinvention could weigh about 0.25 to 5 pounds and could, therefore, beasily mounted on a remote or robotic vehicl for automatically detectingtoxic chemicals or buried explosives or munitions. Alternatively, such adevice would also be useful for remotely detecting explosives vaporsemitting from a p rson intending the destruction of private propertyand/or personnel, such as, for example, at crowded public places likeairports or arenas where terrorist activity may be suspected.

[0056] If desired, it is possible to increase the concentration ofexplosive vapors contained in the area being monitored, i.e., speed uptheir release from buried or otherwise hidden munitions or explosives,by irradiating the area with electromagnetic radiation. For example, abeam-forming antenna could be employed to direct high frequency to longwavelength microwave radiation at the area suspected of containingburied munitions, such as landmines. This will gently warm the areabeing checked and increase explosive vapor leakage prior to testing withthe device of the invention. Increasing the concentration of vapor inthe soil or other environment surrounding a munition will produce astronger signal following the reaction with the sensor portion of thedevice of the invention.

[0057] The chemoselective, hyperbranched compounds of the inventionexhibit high selectivity and sensitivity toward hydrogen bond basicvapors, due to the sensitivity and selectivity of the halogensubstituted alcohol or phenol functional groups that are present. Thefunctionalized hyperbranched compounds of the invention also have theadvantage of high-yield preparation methods, ready purification, inaddition to having an increased availability of functional groups toanalytes, as compared with linear polymeric coatings. Moreover, theflexibility in the synthesis of these materials allows one to tailor awide variety of related chemoselective hyperbranched compounds.

EXAMPLES

[0058] Unless otherwise noted, all synthetic procedures were carried outunder inert atmosphere using standard Schlenk and vacuum linetechniques. Solvents were dried and degassed under an argon atmosphereusing appropriate drying agents.

[0059] These examples are intended to illustrate the present inventionto those skilled in the art and should not be interpreted as limitingthe scope of the invention set forth in the claims.

Example 1 Preparation of [—CH₂—Si(CH═₂CH₂CH₂C(CF₃)₂OH)₂—]_(n)

[0060] To a 500 mL flask containing 2.1 g of Mg chips was added 30 mL offreshly distilled THF. The resulting mixture was cooled to 0° C. andtreated with 10 mL (14.65 g) of ClCH₂SiCl₃ via syringe. The reactionmixture was stirred at 0° C. for four hours with an additional 60 mL ofTHF being added in portions as needed to keep the solution from gettingtoo thick due to salt formation. The reaction mixture was then stirredfor 2 hours at room temperature and treated dropwise with allylmagnesiumbromide (162 mL of 1.0 M in ether) over a two hour period. The resultingsolution was stirred at room temperature for 20 hours. The reaction wasthen quenched with saturated aqueous NHCl and the organic portionextracted with diethyl ether, dried over MgSO₄, and filtered through 1cm of SiO₂. Removal of the volatiles left the product polymer as a paleyellow, viscous oil. A sample of the parent polymer (2.0 g) wasdissolved in CHCl₃ (30 mL) and placed into a mild steel cylinder alongwith a magnetic stir bar. The steel cylinder was then cooled in liquidnitrog n and evacuated. Hexafluoroaceton (˜±4.0 g) was introduced intothe steel cylinder via vacuum transfer. The cylinder was sealed, removedfrom the vacuum line, and heated to 65° C. for 48 hours. The cylinderwas then cooled to room temperature and the volatiles removed undervacuum. Once evacuated, the reaction cylinder was opened to the air, andthe hyperbranched compound inside was extracted with chloroform (4×30mL). The resulting solution was filtered through Celite and thevolatiles removed to give a pale brown polymer. FTIR (NaCl, cm⁻¹) showedthe characteristic OH stretch (˜3510 cm⁻¹) verifying the presence of the—C(CF₃)₂OH groups in the functionalized product.

Example 2 Preparation of [—CH₂—Si{CH₂CH₂CH₂C₆H₃(C(CF₃)₂OH)₂}₂]_(n)

[0061] To a 500 mL flask containing 7.0 g of Mg chips was added 20 mL offreshly distilled THF. The resulting mixture was cooled to 0° C. andtreated with 10 mL (14.65 g) of ClCH2SiCl₃ via syringe. The reactionmixture was stirred at 0° C. for four hours with an additional 60 mL ofTBF being added in portions as needed to keep the solution from gettingtoo thick due to salt formation. The reaction mixture was stirred for 2hours at room temperature then cooled to 0° C. and treated drop-wisewith a THF (60 mL) solution of (3-bromopropyl)benzene (25.5 mL) over atwo hour period. The reaction mixture was then allowed to warm withoccasional cooling to maintain the temperature below 40° C. Theresulting solution was stirred at room temperature for 20 hours. Thereaction was then quenched with saturated aqueous NH₄Cl and the organicportion extracted with diethyl ether, dried over MgSO₄, and filteredthrough 1 cm of SiO₂. Removal of the volatiles left the product polymeras a pale yellow, viscous oil. A sample of the parent polymer (2.0 g)was mixed with a catalytic amount of AlCl₃ (0.1 g) and placed into amild steel cylinder along with a magnetic stir bar. The steel cylinderwas then cooled in liquid nitrogen and evacuated. Hexafluoroacetone(˜4.0 g) was introduced into the steel cylinder via vacuum transfer. Thecylinder was sealed, removed from the vacuum line, and heated to 65° C.for 48 hours. The cylinder was then cooled to room temperature and thevolatiles removed under vacuum. Once evacuated, the reaction cylinderwas opened to the air, and the hyperbranched compound inside wasextracted with chloroform (4×30 mL). The resulting solution was washedwith water, dried over MgSO₄, filtered through Celite and the volatilesremoved to give a pale brown viscous oil. FRIR (NaCl, cm⁻¹) showed an OHstretch (˜3510 cm⁻¹) verifying the presence of the —C(CF₃)₂OH groups inthe functionalized product.

Example 3 Preparation of [—CH₂—Si[CH₂CH═CHC₆H₃(C(CF₃)₂OH)₂}₂]_(n)

[0062] To a 500 mL flask containing 7.0 g of Mg chips was added 20 mL offreshly distilled THF. The resulting mixture was cooled to 0° C. andtreated with 10 mL (14.65 g) of ClCH₂SiCl₃ via syringe. The reactionmixture was stirred at 0° C. for four hours with an additional 60 mL ofTHF being added in portions as needed to keep the solution from gettingtoo thick due to salt formation. The reaction mixture was stirred for 2hours at room temperature then cooled to 0° C. and treated dropwise witha THF (60 mL) solution of cinnamyl bromide (33.0 g) over a six hourperiod. The resulting solution was stirred at room temperature for 20hours. The reaction was then quenched with saturated aqueous NH₄Cl andthe organic portion extracted with diethyl ether, dried over MgSO₄, andfiltered through 1 cm of SiOZ. Removal of the volatiles left the productpolymer as a yellow, viscous oil. A sample of the parent polymer (2.0 g)was mixed with a catalytic amount of AlCl₃ (0.1 g) and placed into amild steel cylinder along with a magnetic stir bar. The steel cylinderwas th n cooled in liquid nitrog n and evacuated. Hexafluoroacetone(˜4.5 g) was introduced into the steel cylinder via vacuum transfer. Thecylinder was sealed, removed from the vacuum line, and heated to 65° C.for 48 hours. The cylinder was then cooled to room temperature and thevolatiles removed under vacuum. Once evacuated, the reaction cylinderwas opened to the air, and the hyperbranched compound inside wasextracted with chloroform (4×30 mL). The resulting solution was washedwith water, dried over MgSO₄, filtered through Celite and the volatilesremoved to give a pale brown viscous oil. FRIR (NaCl, cm⁻¹) showed an OHstretch (˜3510 cm⁻¹) verifying the presence of the —C(CF₃)₂OH groups inthe functionalized product.

Example 4 Preparation of [—(CH₂)₂—Si{CH₂Si{CH═CHCH₂(C(CF₃)₂OH)}₃}₂]_(n)

[0063] To a 500 mL flask containing 6.0 g of Mg chips was added 20 mL offreshly distilled THF. The resulting mixture was cooled to 0° C. andtreated with 10.0 mL (16.69 g) of BrCH₂CH₂SiCl₃ via syringe. Thereaction mixture was stirred at 0° C. for four hours with an additional60 mL of THF being added in portions as needed to keep the solution fromgetting too thick due to salt formation. The reaction mixture wasstirred for 2 hours at room temperature then cooled to 0° C. and treateddropwise with a THF (50 mL) solution of chloromethyltriallylsilane (26.0g) over a four hour period. The resulting solution was stirred at roomtemperature for 24 hours. The reaction was then quenched with saturatedaqueous NH₄Cl and the organic portion extracted with diethyl ether,dried over MgSO₄, and filtered through 1 cm of SiO₂. Removal of thevolatiles left the product polymer as a yellow, viscous oil. A sample ofthe parent polymer (2.0 g) was dissolved in CHCl₃ (30 mL) and placedinto a mild steel cylinder along with a magnetic stir-bar. The steelcylinder was then cooled in liquid nitrogen and evacuated.Hexafluoroacetone (˜4.5 g) was introduced into the steel cylinder viavacuum transfer. The cylinder was sealed, removed from the vacuum line,and heated to 65° C. for 48 hours. The cylinder was then cooled to roomtemperature and the volatiles removed under vacuum. Once evacuated, thereaction cylinder was opened to the air, and the hyperbranched compoundinside was extracted with chloroform (4×30 mL). The resulting solutionwas washed with water, dried over MgSO₄, filtered through Celite and thevolatiles removed to give a pale brown viscous oil. FTIR (NaCl, cm⁻¹)showed an OH stretch (73510 cm⁻¹) verifying the presence of the—C(CF₃)₂OH groups in the functionalized product.

Example 5 Preparation of [—(CH₂)₃—Si(CH═CHCHC₂C(CF₃)₂OH)₂—]_(n)

[0064] To a 50 mL flask was added triallylsilane (2.1 g) andtetraallylsilane (0.1 g) along with 1-2 drops of 0.1 mM H₂PtCl₆(H₂O)_(x)in THF. The resulting mixture was stirred at 50° C. for 18 hoursresulting in a viscous pale yellow oil. The reaction mixture wasdissolved in 20 mL of hexanes and filtered through 1 cm of SiO₂. Removalof the volatiles left the product polymer as a pale yellow, viscous oil.A sample of the parent polymer (1.0 g) was dissolved in CHCl₃ (20 mL)and placed into a mild steel cylinder along with a magnetic stir bar.The steel cylinder was then cooled in liquid nitrogen and evacuated.Hexafluoroacetone (˜3.0 g) was introduced into the steel cylinder viavacuum transfer. The cylinder was sealed, removed from the vacuum line,and heated to 65° C. for 48 hours. The cylinder was then cooled to roomtemperature and the volatiles removed under vacuum. Once evacuated, thereaction cylinder was opened to the air, and the hyperbranched compoundinside was extracted with chloroform (4×30 mL). The resulting solutionwas filtered through Celite and the volatiles removed to give a palebrown polymer. FTIR (NaCl, cm⁻¹) showed the characteristic OH stretch(˜3510 cm⁻¹) verifying the presence of the —C(CF₃)₂OH groups in thefunctionalized product.

Example 6 Preparation of[—(CH₂)₃—Si(CH₂CH₂CH₂C₆H₃(C(CF₃)₂OH)₂)(CH═CHCH₂C(CF₃)₂OH)—]_(n)

[0065] To a 50 mL flask was added 3-phenylpropyldiallylsilane (3.1 g)and allylbenzene (0.05 g) along with 1-2 drops of 0.1 mMH₂PtCl₆(H₂O)_(x) in THF. The resulting mixture was stirred at 50° C. for22 hours resulting in a viscous pale yellow oil. The reaction mixturewas dissolved in 20 mL of hexanes and filtered through 1 cm of SiO₂.Removal of the volatiles left the product polymer as a pale yellow,viscous oil. A sample of the parent polymer (1.5 g) was dissolved inCHCl₃ (30 mL) and placed into a mild steel cylinder along with amagnetic stir bar. The steel cylinder was then cooled in liquid nitrogenand evacuated. Hexafluoroacetone (˜3.5 g) was introduced into the steelcylinder via vacuum transfer. The cylinder was sealed, removed from thevacuum line, and heated to 65° C. for 48 hours. The cylinder was thencooled to room temperature and the volatiles removed under vacuum. Onceevacuated, the reaction cylinder was opened to the air, and thehyperbranched compound inside was extracted with chloroform (4×30 mL).The resulting solution was filtered through Celite and the volatilesremoved to give a pale brown polymer. FTIR (NaCl, cm⁻¹) showed thecharacteristic OH stretch (˜3510 cm⁻¹) verifying the presence of the—C(CF₃)₂OH groups in the functionalized product.

Example 7 Preparation ofco—[—(CH₂)₃—Si(CH₂CH₂CH₂C₆H₃(C(CF₃)₂OH)₂)—]_(m)—[—(CH₂)₃Si(CH═CHCH₂C—(CF₃)₂OH)₂—]_(n)

[0066] To a 50 mL flask was added 3-phenylpropyldiallylsilane (1.8 g),triallylsilane (2.5 g) and tetraallylsilane (0.1 g) along with 1-2 dropsof 0.1 mM H₂PtCl₆(H₂O)_(x) in THF. The resulting mixture was stirred at50° C. for 20 hours resulting in a viscous pale yellow oil. The reactionmixture was dissolved in 20 mL of hexanes and filtered through 1 cm ofSiO₂. Removal of the volatiles left the product polymer as a paleyellow, viscous oil. A sample of the parent polymer (1.5 g) wasdissolved in CHCl₃ (30 mL) and placed into a mild steel cylinder alongwith a magnetic stir bar. The steel cylinder was then cooled in liquidnitrogen and evacuated. Hexafluoroacetone (˜4.0 g) was introduced intothe steel cylinder via vacuum transfer. The cylinder was sealed, removedfrom the vacuum line, and heated to 65° C. for 48 hours. The cylinderwas then cooled to room temperature and the volatiles removed undervacuum. Once evacuated, the reaction cylinder was opened to the air, andthe hyperbranched compound inside was extracted with chloroform (4×30mL). The resulting solution was filtered through Celite and thevolatiles removed to give a pale brown polymer. FTIR (NaCl, cm⁻¹) showedthe characteristic OH stretch (˜3510 cm⁻¹) verifying the presence of the—C(CF₃)₂OH groups in the functionalized product.

Example 8 Preparation of co—[SiCH₂CH₂CH₂Si(CH₂CH₂CH₂C₆H₃(C(CF₃)₂OH)₂)

[0067][CH₂CH₂CH₂Si(CHCH₂CH₂C₆H₃(C(CF₃)₂OH)₂)(CH═CHCH₂C(CF₃)₂OH)_(2-x)(CH₂CH₂CH₂)_(x)—]₂}₄]—[—(CH₂)₃—Si(CH═CHCH₂C(CF₃)₂OH)₂—]_(n)

[0068] To a 100 mL flask was added triallylsilane (2.5 g) and thedendrimeric polymer Si{CH₂CH₂CH₂Si(CH₂CH₂CH₂C₆H₅)[CH₂CH₂CH₂Si(CH₂CH₂CH₂CA)(CH₂CH═CH₂)₂]₂}₄, (0.20 g) along with 1-2 dropsof 0.1 mM H₂PtCl₆(H₂O)_(x) in THF. The resulting mixture was stirred at50° C. for 24 hours resulting in a viscous pale yellow oil. The reactionmixture was dissolved in 20 mL of hexanes and filtered through 1 cm ofSiO₂. Removal of the volatiles left the product polymer as a paleyellow, viscous oil. A sample of the parent polymer (1.0 g) wasdissolved in CHCl₃ (30 mL) and placed into a mild steel cylinder alongwith a magnetic stir bar. The steel cylinder was then cooled in liquidnitrogen and evacuated. Hexafluoroacetone (˜3.0 g) was introduced intothe steel cylinder via vacuum transfer. The cylinder was sealed, removedfrom the vacuum line, and heated to 65° C. for 48 hours. The cylinderwas then cooled to room temperature and the volatiles removed undervacuum. Once evacuated, the reaction cylinder was opened to the air, andthe hyperbranched compound inside was extracted with chloroform (4×30mL). The resulting solution was filtered through Celite and thevolatiles removed to give a pale brown polymer. FTIR (NaCl, cm⁻¹) showedthe characteristic OH stretch (˜3510 cm⁻¹) verifying the presence of the—C(CF₃)₂OH groups in the functionalized product.

Example 9 Preparation ofco—[—(CH₂)₃—Si(Me)O—]_(m)—[—(CH₂)₃—Si(CH═CHCH₂C(CF₃)₂OH)₂—]_(n)

[0069] To a 100 mL flask was added triallylsilane (3.0 g),tetraallylsilane (0.05 g) and poly(methylhydridosiloxane) (0.15 g) alongwith 1-2 drops of 0.1 mM H₂PtCl₆(H₂O)_(x) in THF. The resulting mixturewas stirred at 50° C. for 24 hours resulting in a viscous pale yellowoil. The reaction mixture was dissolved in 20 mL of hexanes and filteredthrough 1 cm of SiO₂. Removal of the volatiles left the product polymeras a pale yellow, viscous oil. A sample of the parent polymer (1.0 g)was dissolved in CHCl₃ (30 mL) and placed into a mild steel cylinderalong with a magnetic stir bar. The steel cylinder was then cooled inliquid nitrogen and evacuated. Hexafluoroacetone (˜3.0 g) was introducedinto the steel cylinder via vacuum transfer. The cylinder was sealed,removed from the vacuum line, and heated to 65° C. for 48 hours. Thecylinder was then cooled to room temperature and the volatiles removedunder vacuum. Once evacuated, the reaction cylinder was opened to theair, and the hyperbranched compound inside was extracted with chloroform(4×30 mL). The resulting solution was filtered through Celite and thevolatiles removed to give a pale brown polymer. FTIR (NaCl, cm⁻¹) showedthe characteristic OH stretch (˜3510 cm⁻¹) verifying the presence of the—C(CF₃)₂OH groups in the functionalized product.

Example 10 Applying a Thin Film to a SAW Device

[0070] SAW devices are cleaned in a Harrick plasma cleaner prior topolymer film application. Spray-coated films of the compound of FIG. 1in chloroform (1% by weight) are applied to a SAW device using anairbrush supplied with compressed dry nitrogen. The frequency change ofthe SAW device operating in an oscillator circuit is monitored duringdeposition, using the change in frequency, typically about 250 kHz, as ameasure of the amount of material applied. After application, the filmsare optionally annealed in an oven at 50° C. overnight. Spray-coatedfilms are examined by optical microscopy with a Nikon microscope usingreflected light Nomarski differential interference contrast.

Example 11 Detection of Basic Vapors with a Compound-Coated SAW Device

[0071] The compounds of FIGS. 1 and 2 are separately applied to SAWdevices and tested against organic vapors at various concentrations.Upon exposure to a vapor, the coated acoustic wave devices undergo ashift in frequency that is proportional to the concentration of thevapor. Times to steady state response, corresponding to equilibriumpartitioning of the vapor into the compound layer, are typically under10 seconds using a vapor delivery system. From frequency shift data fora vapor at multiple concentrations, calibration curves are constructed.The calibration curves are generally linear at moderate concentrations,but deviate from linearity at the high and low concentration levels.Linear calibration curves are consistent with hydrogen-bondinginteractions at a finite number of sites in the compound.

Example 12 Coating a Capillary Column

[0072] A solution of the compound of FIG. 2 in chloroform is used tocoat the interior surface of several one-meter silica capillary columnswith an inside diameter of 100 microns. The procedure to coat a100-micron i.d. column from Fused Silica Intermediate Polarity (partnumber 2-5745, Supelco, Pa.) involves filling the capillary with asolution of the compound, closing one end of the capillary, and pullinga vacuum off the other end of the capillary at a fixed temperature. Thesolution-filled column is placed into a gas chromatographic ovenstabilized at 30° C. to control the temperature. A vacuum is then pulledusing an oil-free Teflon-coated diaphragm pump (Fisher part number13-875-217C), with a vacuum of −70 kPa, typically being applied forabout 15-20 hours.

[0073] The thickness and thickness uniformity are verified by cutting-acoated column into several pieces and looking at the cross sectionsusing a high power optical microscope. The thickness of one micron isusually in good agreement with the theoretical film thicknesses.

Example 13 Optical Fiber Drawing and Cladding

[0074] The compound of FIG. 2 is combined with a solvent to form aviscous mixture, which is stirred until well-blended and degassed undervacuum. The viscous mixture is applied to a fused silica fiber as it isfreshly drawn from a Heathway fiber drawing apparatus through a 2-5 mmSandcliff cladding cup, and into a 45 cm long clamshell furnace forcuring. The viscous mixture is supplied to the cladding cup under apressure of about 0.8 to about 1.5 psi. The optimal furnace temperatureand fiber draw-speed are typically about 520° C. and 8-9 m/minrespectively. These relatively slow draw rates are usually used formanual control of the drawing conditions, but sometimes result invariable core diameters and coating thickness. However, when used withthe other conditions described, a fairly uniform coating that is lightyellow in color and slightly tacky to the touch is usually obtained. Asthe viscosity of the solution of the compound increases during the fiberdrawing, the delivery pressure should be increased over the course offilling, usually about two hours.

[0075] Half-meter to one-meter sections are hand selected for quality.The best fiber sections made under these conditions have a smoothcoating of about 25 microns thick over a 180-micron diameter core. Allare usually effective in guiding light.

[0076] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A hyperbranched polymeric compound having: (1) apolymer backbone portion that is at least partly randomly branched; (2)at least one pendant arm extending from said polymer backbone; and (3)at least one halogen substituted alcohol or phenol group substituted atthe pendant group(s) of the polymer backbone portion.
 2. The compound ofclaim 1 wherein said compound has the general formula:

wherein A is the hyperbranched backbone portion of the polymer; L and Mare independently selected pendant groups of the polymer backbone; X andY are independently selected halogen substituted alcohol or phenolgroups; q and r are independently selected and at least 1; and n is atleast
 3. 3. The compound of claim 2 wherein A is composed of unitsselected from the group consisting of silicon atoms, carbon atoms,siloxane, carbosilane, silylene moieties, and combinations thereof. 4.The compound of claim 2 wherein A is composed of units selected from thegroup consisting of Si-alkylene, Si-arylene, and Si-alkenylene units. 5.The compound of claim 2 wherein L and M are independently selected fromthe group consisting of -alkylene-Si-(alkenylene)₃ and-alkylene-Si-(alkylene-arylene)₃.
 6. The compound of claim 2 wherein: Ais selected from the group consisting of —Si—(CH₂)_(n)—, where n=1-3;—Si—(CH(CH₂C₆H₅))—; and —Si—(CH₂(C═CH₂)CH₂)—; L and M are independentlyselected allyl or propylenephenylene groups; and X and Y arehexafluoroisopropanol groups.
 7. A solution for preparing a chemicalvapor sensor comprising: (a) an amount of a hyperbranched compoundhaving (1) a polymer backbone portion that is at least partly randomlybranched; (2) at least one pendant group extending from the polymerbackbone portion; (3) at least one halogen substituted alcohol or phenolgroup substituted at the pendant group(s) of the polymer backboneportion; effective to enhance the sensitivity of the sensor to hydrogenbond accepting vapors or nitroaromatic compounds; and (b) a solvent forsaid hyperbranched compound.
 8. The solution of claim 7 wherein saidcompound has the general formula:

wherein A is the hyperbranched backbone portion of the polymer; L and Mare independently selected pendant groups of said polymer backbone; Xand Y are independently selected halogen substituted-alcohol or phenolgroups; q and r are at least 1 and independently selected; and n is atleast
 3. 9. The solution of claim 8 wherein A is composed of unitsselected from the group consisting of silicon atoms, carbon atoms,siloxane, carbosilane, silylene moieties, and combinations thereof. 10.The solution of claim 8 wherein A is composed of units selected from thegroup consisting of Si-alkylene, Si-arylene, and —Si-alkenylene.
 11. Thesolution of claim 8 wherein: A is selected from the group consisting of—Si—(CH₂)_(n)—, where n=1-3; —Si—(CH(CH₂C₆H₅))—; and—Si—(CH₂(C—CH₂)CH₂)—; L and M are independently selected allyl orpropylenephenylene groups; and X and Y are hexafluoroisopropanol groups.12. The solution of claim 8 wherein L and M are independently selectedfrom the group consisting of -alkylene-Si-(alkenylene)₃ and-alkylene-Si-(alkylene-arylene)₃.
 13. The solution of claim 7 whereinsaid solvent is selected from the group consisting of hexane,chloroform, dichloromethane, toluene, xylenes, acetonitrile andtetrahydrofuran.
 14. A device for selective molecular recognition, saiddevice comprising a sensing portion, wherein said sensing portionincludes a substrate having coated thereon a layer, said layercomprising a hyperbranched compound having: (1) a polymer backboneportion that is at least partly randomly branched; (2) at least onependant group extending from the backbone portion; and (3) at least onehalogen substituted alcohol or phenol group substituted at the pendantgroup(s) of the polymer backbone.
 15. The device of claim 14 whereinsaid substrate is a surface acoustic wave (SAW) substrate.
 16. Thedevice of claim 14 wherein said compound has the general formula:

wherein A is the hyperbranched backbone portion of the polymer; L and Mare independently selected pendant groups of said polymer backbone; Xand Y are independently selected halogen substituted alcohol or phenolgroups; q and r are at least 1 and independently selected; and n is atleast
 3. 17. The device of claim 16 wherein A is composed of unitsselected from the group consisting of silicon atoms, carbon atoms,siloxane, carbosilane, silylene moieties, or a combination thereof. 18.The device of claim 16 wherein A is composed of units selected from thegroup consisting of Si-alkylene, Si-arylene, and —Si-alkenylene.
 19. Thedevice of claim 16 wherein: A is selected from the group consisting of—Si—(CH₂)_(n)—, where n=1-3; —Si—(CH(CH₂C₆H₅))—; and—Si—(CH₂(C═CH₂)CH₂)—; L and M are independently selected allyl orpropylenephenylene groups; and X and Y are hexafluoroisopropanol groups.20. The device of claim 16 wher in L and M ar independently selectedfrom the group consisting of -alkylene-Si-(alkenylene)₃ and-alkylene-Si-(alkyl n-arylene)₃.
 21. The device of claim 14 wherein saidlayer is deposited on said substrate by a laser-based coating technique.22. A method of detecting the molecules of a hydrogen bond acceptingvapor comprising the steps of: (a) contacting the molecules of saidvapor with a device comprising a sensing portion, wherein said sensingportion includes a substrate having coated thereon a layer, said layercomprising a hyperbranched compound having: (1) a polymer backboneportion that is at least partly randomly branched; (2) at least onependant group extending from the polymer backbone portion; and (3) atleast one halogen substituted alcohol or phenol group substituted at thependant group(s) of the polymer backbone portion. (b) collecting saidmolecules on said layer, wherein said molecules alter a specificphysical property of said layer; and (c) detecting the amount of changein said physical property from before said contacting step (a) and aftersaid collecting step (b).
 23. The method of claim 22 wherein saidsubstrate is a surface acoustic wave (SAW) substrate.
 24. The method ofclaim 22 wherein said compound has the general formula:

wherein A is the hyperbranched backbone portion of the polymer; L and Mare independently selected pendant groups of said polymer backbone; Xand Y are independently selected halogen substituted alcohol or phenolgroups; q and r are at least 1 and independently selected; and n is atleast
 3. 25. The method of claim 24 wherein A is composed of unitsselected from the group consisting of silicon atoms, carbon atoms,siloxane, carbosilane, silylene moieties, and combinations thereof. 26.The method of claim 24 wherein A is composed of units selected from thegroup consisting of Si-alkylene, Si-arylene, or —Si-alkenylene.
 27. Themethod of claim 24 wherein: A is selected from th group consisting of—Si—(CH₂)_(n)—, where n=1-3; —Si—(CH(CH₂C₆H₅))—; and—Si—(CH₂(C═CH₂)CH₂)—; L and M are independently selected allyl orpropylenephenylene groups; and X and Y are hexafluoroisopropanol groups.28. The device of claim 24 wherein L and M are independently selectedfrom the group consisting of -alkylene-Si-(alkenylene)₃ and-alkylene-Si-(alkylene-arylene)₃.